Thank you Patrice.  Your discussion is zoologically sound and as Paul C. says the jelly makes it tougher but this is what the code tries to capture.  My only caveat is that most shell collectors concept of a form is not related to geography but rather variation within populations.  I.e., the albino form, or the elisae form in Regiconus pennaceus.

John
-----Original message-----
From: BAIL PATRICE [log in to unmask]
Date: Mon, 07 May 2007 05:59:41 -0500
To: [log in to unmask]
Subject: forma and variation

Dear Conchlers,

The concept of "form" must be clarified. It is often confused with
individual variation:

Valid species: any population, genetically isolated, without
noticeable intergrades with other neighboring or sympatric
populations. This concept is more biological than morphological and
hard to prove so that in most cases, the stability of phenotypes is
the only source data for determination.

Subspecies: an aggregate of phenotypically similar populations of a
species inhabiting a geographic subdivision of the range of that
species and differing taxonomically from other populations of that
species (Mayr, 1991). Intergrades between subspecies occasionally
appear.

Form: designates specimens with one or more dominant character(s)
closely connected to a geographical area. Often used to indicate
clinal variation.

Varietal names: designates « individual » variation in shape or color.

Form and varietal names have no taxonomic status, but these neutral
terms are very convenient to distinguish phena in many faily of
mollusk. "Forma" here corresponds perfectly to the definition given
by Mayr (1991) for "The Race", a term not mentioned in the Code. The
term variety which is, according to the Code deemed to denote
infrasubspecific rank (after 1960), and which was rejected by Mayr
(1991) is still often used in the malacological literature.


Patrice Bail
2 square La Fontaine 75016 Paris
Tel:+33(1)45253330
Fax:+33(1)40501390

----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------